意識消失発作を契機に発見された胸腔内巨大孤立性線維性腫瘍

Giant Solitary Fibrous Tumor Associated with Loss of Consciousness by Hypoglycemic Attack

孤立性線維性腫瘍（solitary fibrous tumor：SFT）は間葉系細胞由来の比較的まれな腫瘍である．無症状で発見されることが多いが，時に低血糖発作を合併することが報告されており，その原因として腫瘍が産生するインスリン様成長因子（IGF）-Ⅱが関与していると考えられている．われわれは腫瘍からのIGF-Ⅱ産生を証明しえた巨大SFTの手術例を経験したので報告する．

We herein report a rare case of solitary fibrous tumor （SFT） producing high-molecular-weight insulin-like growth factorⅡ（big IGF-Ⅱ）. A 51-year-old woman with a large mass in the right thorax suffered from repeated loss of consciousness due to hypoglycemic attack. A hematological examination revealed low values of serum insulin and C-peptide despite her hypoglycemia. We therefore regarded her giant thoracic tumor as the cause of the hypoglycemic attack. She underwent resection of the tumor and was diagnosed with SFT pathologically. After the surgery, her blood sugar level stabilized immediately, and she has had no hypoglycemic attacks since. Although we identified big IGF-Ⅱ in a preoperative serum sample by a Western immunoblot analysis, it was not detected after surgical resection. Positivity for big IGF-Ⅱ was observed in the tumor cells by immunohistochemical staining. We therefore concluded that big IGF-Ⅱ produced by the SFT caused the hypoglycemic attack in this patient.